Comparison of the skin irritation potential of two testosterone transdermal systems: an investigational system and a marketed product

Effective transdermal therapy provides controlled release of the appropriate amount of a therapeutic agent while minimizing local irritation. Transdermal administration of testosterone has the potential to produce skin irritation. This open-label, randomized, 14-day, outpatient study compared the skin irritation of an investigational testosterone transdermal system (System I) with that of a marketed testosterone transdermal system (System II) in healthy men. In Part 1 of the study, System I was applied 10 times over 14 days to the same skin site on the backs of 26 healthy men. In Part 2, the skin irritation resulting from daily application of Systems I and II was assessed over 14 days in 17 men less than 65 years of age and 16 men 65 years of age or older. At the end of Part 1 of the study, 65.4% of the subjects experienced no erythema, 15.4% of subjects had faint erythema, and 19.2% had moderately intense erythema immediately after System I removal. At the completion of Part 2, none of the System I application sites were assessed as having moderately intense erythema, whereas one third (33.3%) of System II application sites demonstrated moderately intense erythema. There were no differences in erythema rates between younger and older subjects with either transdermal system. During this study, repeated application of System I to the same skin site resulted in acceptable noncumulative irritation, suggesting that application-site rotation may not be necessary. A comparison of the two systems demonstrates that System I results in significantly less application-site irritation than does System II and that older men do not have a higher rate of skin reactions.